1. Technical Field
The present invention relates to an electro-optical device for emitting a light modulated in a condition which is associated with an electrical signal, and an electronic apparatus and a projection display device including the electro-optical device.
2. Related Art
In a projection display device called a projector or the like, a liquid crystal device used as a light valve is constituted as an electro-optical device for emitting a light modulated in a condition which is associated with an electrical signal. Among the electro-optical devices, in a case of a transmissive liquid crystal device, a liquid crystal panel receives light entering from one surface, spatially modulates this light, and emits the modulated light from another surface. On the other hand, in a case of a reflective liquid crystal device, the liquid crystal panel receives light entering from one surface, spatially modulates this light, and emits the modulated light from another surface.
Generally, these liquid crystal panels use a quartz substrate as an element substrate, and have a structure forming field effect transistors or the like on this element substrate. A semiconductor layer which is a channel layer of the field effect transistor is formed using a method of crystallizing after depositing on the quartz substrate using a thin-film forming technique or a method using a substrate with a SOI structure attaching a single crystal silicon film on the quartz substrate. Since the latter uses a single crystal Si having a superior crystallinity, and the field effect transistor may be formed to have a high mobility and also few characteristic variations, and it is relatively easily possible to correspond to a circuit driving having a high driving frequency such as a multi-pixel, multi-gray scale, or digital driving. Also, since the former uses a single crystal Si having a superior crystallinity, a field effect transistor may be formed to have a high mobility and also little variability in characteristics.
The digital driving is a method for representing an intermediate gray scale by applying 0 V or 5 V to a liquid crystal layer at respective subfields obtained by dividing an image signal of one field ( 1/60 second) into a plurality of subfields (for example, refer to JP-A-2001-100180).
In the electro-optical device according to JP-A-2001-100180, a liquid crystal used as an electro-optical material changes response speed to a voltage according to temperature. Thereby, in the case of using the digital driving mode described above, if the temperature of the liquid crystal panel changes, it distorts the gradation property of a displayed image and causes occurrence of poor display. For example, if the temperature change in an atmosphere provided with the projection display device, or the amount of an illumination light supplied from a high brightness lamp to the liquid crystal device is adjusted using a diaphragm or the like depending on the displayed image, as the result of the occurrence of temperature change in the liquid crystal panel and a distortion of the gray scale, it is impossible to obtain a smooth display due to occurrence of a display unevenness or the like. On the other hand, if a temperature sensor is subsequently attached in the vicinity of the element substrate, there is a problem in that the liquid crystal temperature cannot be accurately monitored due to separation of the temperature sensor from the liquid crystal as well as cost increases.